Method for manufacturing a sound insulating structure and the structure produced thereby

ABSTRACT

The present invention provides a sound insulating structure cover panel that compliments the sound attenuation material. The method of manufacturing the panel includes the steps of providing a laminated blank having an interior face which will be observable from the passenger compartment. The side opposite the interior face of the blank has a generally non-permeable polymeric layer adjacent to a primary backing and a secondary backing layer overlying the polymeric layer. In the preferred process, the previously described blank is elevated to a desired temperature and positioned in a closed forming mold such that the perimeter of the blank is retained in a fixed position. The forming mold is closed with a controlled pressure that is sufficient to expand the blank, conform it to the mold and render a panel having a desired permeability.

BACKGROUND

This application is a divisional of U.S. patent application Ser. No.09/266,155, filed Mar. 10, 1999, which is specifically incorporatedherein by reference.

The present invention generally relates to trim panels used to cover theinterior surfaces of a vehicle. The invention more particularly relatesto panels used to cover the interior surfaces of a passenger vehiclewhere sound attenuation is desired. The invention most particularlyrelates to panels which are used in passenger vehicles where appearanceand sound attenuation are required. Such panels are employed as the headliners, wall liners and carpets of a vehicle for the purpose ofimproving appearance, temperature and sound control while enhancing thepassengers' driving pleasure.

The use of trim panels and carpet panels to provide passenger comfortare well known in the art. For example, see U.S. Pat. Nos. 4,741,945;4,508,774; and 5,334,338. In addition, the use of these knownmanufacturing techniques employed by the present invention for producingstandard floor covering is also known. See U.S. Pat. No. 5,855,981.

Early efforts at sound attenuation in vehicles generally relied uponheavy, dense materials which would resist the entry of exterior noisesinto the passenger cabin. However, experience with such materials led toconcerns about the transmission of vehicle vibrations and other soundsbased upon the heavy insulating materials. Accordingly, the art hasrecently considered the use of ultralight, multifunctional,sound-insulating materials. For example, see WO 98/18656 and WO98/18657.

More recently, it has been determined that ultralight, multifunctional,sound-insulating materials may not achieve their full benefit when usedwith exterior cover materials that do not compliment their function.Accordingly, the art desired an exterior or decorative cover materialwhich permitted controlled sound transmission to the interior of thevehicle. It has been theorized that permitting transmission of somesound into the cabin will result in sound cancellation and a morepleasing passenger environment. As a result of the more pleasingenvironment, the use of ultralight materials will be greatly enhancedand a reduction in vehicle weight will be recognized without anydecrease in cabin comfort.

SUMMARY

The present invention provides a sound insulating structure cover panelthat compliments the sound attenuation material. The method ofmanufacturing the panel comprises the steps of providing a laminatedblank having an interior face which will be observable from thepassenger compartment. The side opposite the interior face of the blankhas a generally non-permeable polymeric layer adjacent to a primarybacking and a secondary backing layer overlying the polymeric layer. Inthe preferred process, the previously described blank is elevated to adesired temperature and positioned in a closed forming mold such thatthe perimeter of the blank is retained in a fixed position. The formingmold is closed with a controlled pressure that is sufficient to expandthe blank, conform it to the mold and render a panel having a desiredpermeable. Preferably, the post formation panel has a permeability of500 rayls or less as measured on concentric airflow resistance equipment(C.A.R.E. unit) available from Rieter Automotive North America, Inc.38555 Hills Tech Drive, Farmington Hills, Mich. 48331.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a known carpet construction which is suitable for usewith the present invention.

FIG. 2 is an enlargement of the construction within the phantom lines ofFIG. 1.

FIG. 3 is an enlargement, similar to FIG. 2, showing the wicking-in ofthe polymeric layer in the construction of the present invention asdescribed in the exemplary embodiment of FIG. 1.

FIG. 4 illustrates the wicking-in of FIG. 3 within the tufts of yarn.

FIG. 5 illustrates a continuous operation for stretching and molding apanel in accordance with the present invention.

FIG. 6 illustrates a heating table for use with a preferredmanufacturing process.

FIG. 7 illustrates a mold assembly in accordance with the invention.

FIG. 8 illustrates a panel in the final molding and cooling stage.

FIG. 9 illustrates a molded and cooled panel prior to trimming.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The invention will be described with reference to the drawing figureswherein like numbers indicate like elements throughout. It will beappreciated by those skilled in the art that the drawing figures are notto scale and liberties have been taken to permit illustration of theinvention.

With reference to FIG. 1, there is shown a material blank 2 wherein abacking layer 10, of woven or non-woven construction, is used as asupport base for a plurality of yam tufts 12. Each of the yam tufts 12is comprised of a plurality of yarns in either a spun or filamentconstruction. After the insertion of tufts 12 into the backing 10, thetufted assembly may be subjected to color and finishing operationsbefore an extrusion coating process which places a polymeric layer 14 onthe underside thereof. Finally, a backing layer 16, generally a porous,non-woven material, is applied to the polymeric layer 14. Thisconstruction will be known to those in the art. As a result of thisconstruction, the resulting laminate will have a face surface 18 whichwill be the interior surface and a backing surface 20 which will be theexterior surface. For use in the automotive industry, the laminatedmaterial is cut into a blank that is subjected to a molding process forproducing a post formation panel of a desired geometry in accordancewith the vehicle body geometry. Such a construction is known to thoseskilled in the art and does not form any part of the present invention.

Although the above-described construction of the laminate and the panelsare known to those skilled in the art, the present invention differsfrom the known constructions in the selection of materials for polymericlayer 14 and the post formation process parameters used to form thepanels. In keeping with the present invention, the polymeric layer 14 iscomprised of a high melt flow polymer which will provide the desiredresponse to the subsequent processing in accordance with the invention.Test materials and panels used to demonstrate the present invention aredescribed below.

The tufted assemblies used for testing were produced by tuftingcontinuous filament yarns of 1400 denier or 1405 denier BCF nylon yamsinto non-woven primary backing substrates of 120 g/m²-140 g/m² polyesterfiber. If desired, spun or other yarn constructions may be used. Tuftingmachine gauges of ⅛ gauge and {fraction (1/10)} gauge have beenevaluated. It will be recognized by those skilled in the art thatmachine gauge stitches per inch and stitch pile height combine todetermine the overall carpet construction and density. The number ofpenetrations per square inch is a factor in determining the availableporosity and the wicking-in ability of the construction. The availableporosity is an important aspect of the invention because the finalproduct of the preferred embodiment must meet the aesthetic anddurability standards set by the vehicle manufacturer. As theconstruction is altered, the percentage of expansion to achieve thedesired post formation product may need to be modified.

The tufted assemblies of the tests were extrusion coated, using knowntechniques, with a low density polyethylene coating 14 and laminatedwith a light weight secondary non-woven polyester substrate. Apolyethylene coating 14, of AT 193, available from A. T. Plastic, Inc.of Ontario, Canada, applied between 375-400 g/m² has been usedsuccessfully with a known 13-17 g/m² secondary polyester substrate 16.

The secondary substrate 16 is laminated directly to the polyethylene 14using a standard nip roll, in accordance with prior practices. Thetemperature of the polyethylene extruding from the die is approximately400° F. The nip pressure, for a laminate of approximately 0.250 inches,at the rolls was approximately 50 pounds per linear inch and the nipsetting was approximately 0.030 inches. The chill roll temperature wasin the range of 55-70° F., and the process line speed varied between25-40 FPM. At this point, the laminated material was either rolled up orcut into blanks in preparation for the molding operation. Although thislaminated material is still non-permeable, it is correctly prepared forthe subsequent process which will render it permeable.

In order to form a finished panel, a specific blank size was cut andheated prior to molding. Through reheating of the carpet laminate, thepolymeric layer 14 begins wetting out or wicking-in, see FIGS. 3 and 4.This causes the polymeric layer 14 to flow into the tufts 12 and createsvoids 15 between the tufts 12. This is the beginning of thetransformation from a non-permeable to a permeable laminate. The voids15 that are formed in the polymeric layer 14 result in the laminatebeing permeable. The transformation to the desired permeability wasachieved by stretching, molding and curing the heated laminate.

Heating of the material 2 for 25-30 seconds under a heat intensity of 10to 15 watts per square inch of material has been found to provide asatisfactory temperature elevation with the test material. By heatingthe back surface 20 to a temperature between 325°-350° F., the polymericlayer 14 can be worked without causing melt flow or a loss of adhesion.The heated blank was molded in a chilled molding tool at approximately1.5 to 4.0 PSI of mold pressure and 45° F. The approximate cool downtime in the molding tool was forty-five (45) seconds. In the testmaterial, these conditions produced a controlled stretch of seven to tenpercent (7-10%) of the blank size. Upon removal from the mold, a facepanel with the desired air permeability had been produced.

With reference to FIGS. 5 through 9, the manufacturing process, as usedto produce test samples and as envisioned for production quantities,will be described. As illustrated in FIG. 5, the material moves from asupply roll to a heating table (FIG. 6) through a mold (FIGS. 7 and 8)and is off loaded or further processed as a panel (FIG. 9).

In FIGS. 5 and 6, a supply roll 40 of laminated blank material 2 issecured to a tenter frame 46 which has material retaining means 48spaced in accordance with the desired blank perimeter. The retainermeans 48 may be pins, clips or other holding means to grip the materialand establish the length and width of the blank. They preferably areadjustable or removable to provide a cutting gap 50 where a transversecutter 51 can cut the blank from the supply roll 40. The blank passesover the heating table 52 beneath a plurality of heating elements 54which are selected in accordance with the construction of the laminatedblank material 2 so as to achieve the desired temperature. It isexpected that the elements at the entrance 56 will be selected torapidly elevate the temperature while the elements at the exit 58 willbe selected to achieve equalization at a desired temperature.

In FIG. 7, the heated panel 60 is presented to the refrigerated mold 62which has a movable, pressure applying half 64 and a stationaryrefrigerated half 66. While being held by the retainers 48, the blank 60is aligned over the mold as it is closed at the desired pressure tostretch the generally planar blank 60 over the contour of the mold. Itwill be recognized by those skilled in the art that the mold 62 isconfigured, in both halves 64 and 66, to the geometry of the vehiclesfloor board. When the mold 62 is finally closed, as illustrated in FIG.8, the blank 60 might be repositioned in the mold 62, however, theoriginal perimeter of the blank will remain substantially unchanged.After the molded panel 70 is released from the mold, FIG. 9, it maycontinue to a subsequent processing operation as described hereinafter,or the perimeter may be trimmed to provide a finished and cut to sizemolded panel.

The test samples produced for this invention were made with the use ofpiece goods that were presented to the heating table and molded througha hand operation. In this operation, the heated blank was manuallyplaced over a stationary tenter frame adjacent to the mold and the moldwas manually emptied when the stretching and molding operation had beencompleted.

Permeability of the test samples was established by using a C.A.R.E.unit. On average, three readings were taken in four locations on eachsample to establish that the panel had achieved the desiredpermeability. Generally, for automotive purposes, it is preferred totake the test reading in the flat of the foot wells or the base of thepanel. In any event, it is preferred that the reading be taken in anarea more representative of the mold extension. Thus, a flat portiondirectly over the tunnel may not be fairly representative. In additionto the above, the use of a well base also provides the practicaladvantage of being accessible and supportable. It is important tosupport the sample on a firm but open surface, such as a mesh table,that will not restrict air flow, so the test equipment can be appliedfirmly.

As noted previously, this invention was motivated by the desire toenhance the use of ultralight material as described in W98/18656 andWO98/18657. The description of that material is incorporated herein asif fully set forth. In keeping with the effort to achieve the maximumbenefits of this combination, the assembly of the panel 70 to theultralight material will be described. Since the combined componentsmust maintain the permeability of the entire sound insulation assemblywithin a specified range, they must be carefully adhered together. Oneacceptable adhesive is available from National Starch as item 34-3378with a melt viscosity of 1500-2125 centapoise at an applicationtemperature of approximately 400° F. An application of hot melt adhesivein the range of 7-9 gm/Ft.2 has found to be successful in adhering thecomponents while maintaining the desired permeability.

The adhesive which may be applied to either the carpet or the insulator,preferably, is in a randomized web. This randomized application assuresadhesive bonding in all areas without restricting the permeability. Thetwo components should be aligned for accuracy before bonding to preventmultiple positioning attempts which diminish the adhesion and disturbthe permeability. The assembly press used to assure physical bonding ofthe components has preset stops which limit the forces on the componentsand prevents compression of the sound insulator beyond that needed foradhesion and maintains the assembly's permeability characteristics.Based on the test samples, the assembled components should be compressedwith a force that will not compress the ultralight material beyond itsspecified finished part thickness by more than 2 mm. This avoids acompression from which the ultralight material may not rebound.

It will be recognized by those skilled in the art that the automotiveindustry has specifications and test methods for product performance anddurability that must be met by the product in the field. The panelsproduced in accordance with the present invention have met these productand test specifications.

We claim:
 1. A process for manufacturing a sound insulating carpetstructure comprising: providing a textile material having interior andexterior sides, a generally non-permeable polymeric layer overlying theexterior side, and a backing layer overlying the polymeric layer to forma laminated product; presenting the laminated product having an initialsurface area to a forming mold having a greater surface area thatretains the perimeter of the laminated product in a fixed positionrelative to the mold; closing the forming mold under a controlledpressure, heat and time cycle sufficient to expand the laminated productto conform to the mold and form voids in the polymeric layer to renderthe laminated product permeable with a permeability of no more than 500rayls (N s/m³); and curing the permeable laminated product.
 2. A processfor manufacturing a sound insulating structure comprising a textilepanel having interior and exterior faces, a generally non-permeablepolymeric layer overlying the exterior face and a backing layeroverlying the polymeric layer, comprising the steps of: preheating thepanel to a controlled temperature; positioning the preheated panel in aforming mold such that the perimeter of the panel is retained in a fixedposition relative to the mold; closing the forming mold with controlledpressure sufficient for expanding the panel to conform it to the moldand form voids in the polymeric layer to produce a permeability of 500rayls (N s/m³) or less as measured by concentric airflow resistanceequipment through the panel; and allowing the panel to cool.
 3. Aprocess for manufacturing a permeable laminated product from a generallynon-permeable laminated sound attenuation panel comprising: a) providinga generally non-permeable laminated sound attenuation panel of textilematerial having interior and exterior sides, a non-permeable polymericlayer overlying the exterior side and a backing layer overlying thepolymeric layer; b) heating the laminated sound attenuation panel of a)to a sufficient temperature to cause the polymeric layer to flow intothe textile material; c) presenting the product of b) to a forming moldthat fixes its perimeter relative to the mold; and d) closing theforming mold under a controlled pressure, heat and time cycle sufficientto conform the product of c) to the mold, while maintaining itsperimeter fixed, and form voids in the polymeric layer to render anexpanded permeable laminated product having a permeability of no morethan 500 rayls (N s/m³).
 4. The process of claim 3 wherein the textilematerial comprises an assembly of continuous filament yarns tufted intoa backing substrate.
 5. The process of claim 3 further comprising thestep of cooling the laminated product to 55-70 degrees F. before heatingthe laminated product.
 6. The process of claim 3 wherein the step ofheating the laminated product comprises heating the laminated productfor 25-30 seconds under a heat intensity of 10-15 watts per square inchof the laminated product.
 7. The process of claim 3 wherein thecontrolled pressure, heat and time cycle comprises 1.5-4.0 PSI ofpressure at a temperature of about 45 degrees F. for about 45 seconds.8. The process of claim 3 wherein the sound attenuation panel isexpanded by 7-10 percent over the laminated product.
 9. The process ofclaim 3 wherein the forming mold is refrigerated.
 10. The process ofclaim 3 wherein heating step causes wicking of the polymeric layer intothe textile material.
 11. A process for manufacturing a soundattenuation panel comprising: providing a textile material havinginterior and exterior sides, a polymeric layer overlying the exteriorside and a backing layer overlying the polymeric layer to form agenerally non-permeable laminated product; heating the laminated productfor 25-30 seconds under a heat intensity of 10-15 watts per square inchof laminated product to cause wicking of the polymeric layer into thetextile material; presenting the laminated product to a forming moldsuch that the perimeter of the laminated product is retained in a fixedposition relative to the mold; refrigerating the forming mold to atemperature of 45 degrees F.; and closing the forming mold under 1.5-4.0PSI of mold pressure for about 45 seconds to conform the laminatedproduct to the mold and form voids in the polymeric layer to render apermeable sound attenuation panel that is expanded by 7-10 percent overthe laminated product.